1. Field
The present disclosure relates to chemical polishing solutions and chemical polishing methods using the chemical polishing solutions for gallium arsenide (GaAs) wafers.
2. Description of Related Information
GaAs is an important semiconductor material, developed more recently than Ge and Si to meet performance demands in semiconducting and semi-insulating devices. In certain applications and fields, GaAs crystals perform better than Ge and Si. For example, GaAs has an electron mobility about 6 times higher and can operate at higher frequencies than Si, and is thus a good material for high-speed integrated circuits and electronic devices. Monocrystalline GaAs wafers are mainly used in microwave and mm-wave communication fields, such as mobile phone, satellite transmission broadcast, radar system and other related areas of advanced electronics. Owing to its excellent photoelectric properties, GaAs is also used extensively in laser devices and light emission diode (LED) applications. Developments in these technologies coupled with the expanding use of monocrystalline GaAs has fostered a rapid increase in demand for GaAs products of higher quality and lower cost. GaAs manufacturers have made efforts to improve product quality and reduce cost, including attempts to reduce adverse environmental impacts such as pollution stemming from chlorine (Cl2) volatilization of wafer polishing solutions.
In general, GaAs wafers are cut from a GaAs crystal ingot by a metal saw or a wire saw, which then undergo further processing, including grinding, chemical mechanical polishing, chemical polishing, and special cleaning before being packaged for delivery. The processed GaAs crystal wafers have smooth, mirror-like main surfaces. Consumers of these processed GaAs crystals typically add different monocrystalline layers of various thicknesses onto the surface to provide devices with different functions.
During the chemical mechanical polishing and chemical polishing processes, polishing solutions are used, which are referred to as “chemical polishing solutions.” The existing chemical polishing solutions often leave the GaAs crystal wafers contaminated with metal ions. Accordingly, electrical devices prepared using these wafers may suffer a variety of drawbacks and defects such as increased leakage current, reduced service life, and failures, and the like. As such, there is a need in the art for improved chemical polishing solutions that enable creation of GaAs crystal wafers of high quality, while minimizing production costs, pollution and/or related problems.